Ecological weed management and square planting influenced the weed management, and crop productivity in direct-seeded rice

Herbicide use may pose a risk of environmental pollution or evolution of resistant weeds. As a result, an experiment was carried out to assess the influence of different non-chemical weed management tactics (one hoeing (HH) at 12 DAS followed by (fb) one hand weeding at 30 DAS, one HH at 12 DAS fb Sesbania co-culture and its mulching, one HH at 12 DAS fb rice straw mulching @ 4t ha−1, one HH at 12 DAS fb rice straw mulching @ 6 t ha−1) on weed control, crop growth and yield, and economic returns in direct-seeded rice (DSR). Experiment was conducted during kharif season in a split-plot design and replicated thrice. Zero-till seed drill-sown crop (PN) had the lowest weed density at 25 days after sowing (DAS), while square planting geometry (PS) had the lowest weed density at 60 DAS. PS also resulted in a lower weed management index (WMI), agronomic management index (AMI), and integrated weed management index (IWMI), as well as higher growth attributes, grain yield (4.19 t ha–1), and net return (620.98 US$ ha–1). The cultivar Arize 6444 significantly reduced weed density and recorded higher growth attributes, yield, and economic return. In the case of weed management treatments, one HH at 12 DAS fb Sesbania co-culture and its mulching had the lowest weed density, Shannon-weinner index and eveness at 25 DAS. However, one hoeing at 12 DAS fb one hand weeding at 30 DAS (HH + WH) achieved the highest grain yield (4.85 t ha–1) and net returns (851.03 US$ ha–1) as well as the lowest weed density at 60 DAS. PS × HH + WH treatment combination had the lowest weed persistent index (WPI), WMI, AMI, and IWMI, and the highest growth attributes, production efficiency, and economic return.

lower weed densities of grasses, sedges, broadleaf, and total weeds, respectively, than P N .Lower weed densities in P S geometry may be due to weed growth smothering as a result of uniform plant-to-plant and row-to-row spacing 30,36 .Square planting further encourages crops to compete with weeds as a result of the better availability of space, light, and nutrients 18,37,38 .Nichols et al. 39 , and Dass et al. 13 , reported that a uniform row-to-row and plant-to-plant distance in rice had a lower weed-competition.Among cultivars, Arize 6444 (hybrid from Bayer) was more competitive with weeds than PHB 71 (hybrid from Pioneer) at 25 and 60 DAS.Faster emergence and robust seedlings of Arize 6444 were thought to be reasons for increased competitiveness.The cultivars that achieve early vegetative vigor and quick ground cover have a competitive advantage over weeds compared to varieties that have slow initial growth 35,40 .With regards to weed management treatments, H H + S C had the lowest grass, broad-leaf, sedge, and total weed densities at 25 DAS, with reductions of 90.61%, 91.81%, 89.05%, and 90.19%, respectively, compared to the weedy check.
However, H H + W H treatment had the lowest weed densities at 60 DAS with 92.77%, 46.77%, 58.52% and 53.64% lower densities of grassy, broad-leaf, sedges, and total weeds compared to the weedy check.Further, treatments H H + M R4 and H H + M R6 recorded lower weed densities than W C at both the stages.Early prevention and suppression of weed germination and growth could be the reason for the lowest weed density in the H H + S C treatment.Keeping the weeds free at an early stage (hand hoeing at 12 DAS) and during the peak weed emergence period (manual weeding during the active tillering stage at 30 DAS) might have resulted in reduced weed competition and weed density of all the weeds at later stages 12,18 .
Interaction of planting geometry (PG) × cultivar (CV), CV × weed management (WM), and PG × CV × WM did not influence the weed density at 25 and 60 DAS (Table 1).However, planting geometry × weed management significantly (p < 0.05) influenced the broadleaf, sedge, and total weed densities at 25 DAS, and broadleaf weed density at 60 DAS (Table 1).The interaction of PG × WM revealed that P N and H H + S C combinations resulted in Table 1.Weed density influenced by planting geometry, cultivar, and non-chemical weed management in rice.*The data in the parentheses are original data; means with different alphabets are significant (p < 0.05).† Values shown are square-root [√(x + 0.5)] transformed means.DAS, days after sowing.P N , sowing with seed drill at 18.5 cm row spacing; P S , square planting at 25 cm × 25 cm row to row and plant to plant spacing; W C , weedy check (no weed management); H H + W H , one hand hoeing at 12 DAS fb one hand weeding at 30 DAS; H H + S C , one hand hoeing at 12 DAS fb S. aculeata co-culture and mulched 45 DAS; H H + M R4 , one hand hoeing at 12 DAS fb rice residue mulching @ 4 t ha −1 ; H H + M R6 , one hand hoeing at 12 DAS fb rice residue mulching @ 6 t ha −1 .**Bold P values are significant.www.nature.com/scientificreports/ the lowest broadleaf, sedge, and total weed densities (Fig. 1a,b).This could be due to the lack of space available for weed growth in close spacing and smothering effect of sesbania co-culture treatments 18,41 .The lowest broadleaf density at later stage under P S and H H + W H combinations may be due to keeping the plots weed free in hand hoeing fb hand weeding treatments and faster crop growth when planted in the square pattern.

Weed diversity indices
Weed diversity indices such as dominance, evenness, and diversity were not influenced by PG, CV, or their interaction (Table 2).However, weed management (WM) had a significant effect on all the weed indices at 25 and 60 DAS.The H H + S C weed management treatment had the lowest Shannon-Wiener and evenness indices but the highest dominance index (Table 2).The lowest Shannon-Wiener and evenness indices values in H H + S C treatment indicate greater control of weeds 42 .Data on evenness (close to 1) indicates that weed species distribution in this experiment is more uniform across treatments.Weed evenness was not influenced by the interaction between PG and CV and PG, CV and WM at either evaluation date (25 or 60 DAS).However, at 25 DAS, PG × WM and CV × WM had a significant effect on evenness (Fig. 2a,b).Likewise, at 60 DAS, the interaction of PG × WM and CV × WM had a significant effect on evenness (Fig. 2b,c), dominance (Fig. 3a,b), and the Shannon-Wiener index (Fig. 3b,c).Compared to other treatments, Ps and the H H + S C combination had significantly lower values of evenness and Shannon-Wiener index and the highest dominance value.

Weed control efficiency indices
Planting geometry had a significant effect (p < 0.05) on WMI, AMI, and IWMI, but did not influence the CRI and WPI (p > 0.05, Table 3).Compared to the zero-till seed drill sown method, the square planting (P S ) method had a lower WMI, AMI, and IWMI, which indicates the effectiveness of this method on weed suppression.The lowest values of WMI, AMI, and IWMI indicate better weed control and a higher yield.The lowest values of WMI and AMI were recorded in earlier studies by Mishra et al. 43 and Kumar et al. 24 with treatments that efficiently reduced weeds and increased grain yield.
Cultivars influenced the CRI significantly (p < 0.05) compared to other indices.The cultivar Arize 6444 resulted in a higher CRI value than the cultivar PHB 71.CRI indicates increased vigor of crop plants due to weed control.Superior crop growth and biomass production of the Arize 6444 cultivar could be the reason for the higher CRI value.Garko et al. 44 also reported a significant effect of different varieties on CRI in maize crop.The weed management treatments greatly influenced all the weed management indices.Among weed management treatments, H H + W H performed well; therefore, this treatment had a 169% higher CRI than the weedy check.
Furthermore, H H + W H treatment resulted in the lowest values of WPI, WMI, AMI, and IWMI over other treatments.The lower WPI, WMI, AMI, and IWMI indicate superior weed control.
The interaction effect of planting geometry × weed management revealed that P S × H H + W H had a lower value of WPI, WMI, AMI, and IWMI (Fig. S2a).Square planting and hand hoeing at the early stage fb hand weeding at peak weed emergence period could have resulted in better weed control than other combinations.The interaction of cultivar × weed management only had a significant effect on CRI (Fig. S2b).Greater suppression and control of weeds under the combination of Arize 6444 × H H + W H treatment might have led to a higher CRI.

Crop growth parameters
Planting geometry, cultivar, and weed management influenced the crop growth parameters (Table 4).However, the interaction effect of planting geometry, cultivar, and weed management did not influence except the number of tillers by planting geometry-by-cultivar and dry matter production by cultivar-by-weed management.The number of tillers (number m −2 ) and dry matter production (g running m −1 ) were (p < 0.05) 7.6% and 13.11% higher, respectively, for the square planting (P S ) compared to the zero-till seed drill sown crop (P N ).This could be due to optimum crop spacing that allowed the radiant energy, nutrients, and water to utilize; as a result, more tillers and robust crop growth were achieved under the square planting method 6 .On the other hand, De Datta 45 , reported that a higher seed rate in a seed drill-sown crop with normal spacing increases inter-and intra-plant competition, which leads to poor utilization of applied inputs, poor crop growth, and a lesser number of tillers.Furthermore, the square planting treatment decreased weed competition compared to zero-till seed drill-sown crop; this could also be the reason for the better growth and development.Cultivars only influenced the dry matter accumulation but not the number of tillers (Table 4).The Arize 6444 resulted in 8.41% higher dry matter production than the PHB 71; the higher dry matter for Arize 6444 could be the result of greater plants height and tiller production 46 .The weed management treatments, H H + W H and H H + S C resulted in the highest number of tillers and dry matter compared to other weed management treatments (Table 4).Hoeing and hand weeding at the early phases of crop growth might have nullified the early weed competition and ultimately led to a greater number of tillers and dry matter.Our findings are in agreement with Johnson et al. 47 who reported that early-stage weed control in direct-seeded rice reduced weed pressure and increased grain yield.Growing S. aculeata and retaining its mulch in rice can suppress the weeds effectively 48 .Additionally, mineralization of residues provides available nutrients to crops at critical stages, which has a positive effect on crop growth at an early stage 49,50 .
Planting geometry × weed management had a significant effect on the number of tillers.The interaction effect of P S and H H + W H resulted in a maximum number of tillers, followed by P N and H H + S C and P N and H H + M R treatment combinations (Fig. 4a).Cultivar × weed management was found significant for dry matter accumulation.Arize 6444 and H H + W H , Arize 6444 and H H + S C combinations had a higher dry matter accumulation (Fig. 4b).The authors believed that this could be due to the synergistic effect of wider spacing in square planting and control of weeds by hand hoeing fb hand weeding, and hand hoeing fb Sesbania co-culture treatments.

Crop productivity
Compared to zero-till seed drill-sown crop (P N ), square planting (P S ) achieved a ~ 7.6% higher grain yield (Table 4).Vigorous crop growth, minimum inter-specific competition, a higher number of tillers, and greater weed suppression might be responsible for higher yields in the square planting method 12,18,51 .Previous studies reported that direct-seeded rice in the square planting method had a higher grain yield compared to normal planting 52 .Among cultivars, Arize 6444 produced a 10.7% higher grain yield than PHB 71.The higher grain yield for Arize 6444 could be attributed to increased dry matter accumulation, more tillers, faster crop growth, and better weed suppression 15 .With respect to weed management tactics, the H H + W H recorded the highest grain yields (4.85 t ha −1 ), followed by the H H + S C (4.68 t ha −1 ).Hoeing fb hand weeding during the critical cropweed competition period might have reduced the weed competition and led to better crop performance 14,53 .
Early weed control is crucial in DSR for improved crop growth and yield 5,6 .The hand hoeing fb either hand weeding or Sesbania spp.co-culture resulted in a weed-free condition and improved yield.Similarly, Maity and Mukherjee 49 , also reported that co-culture of Sesbania with rice smothered weeds and enhanced the grain yield of rice.Likewise, Baumann et al. 27 , and Gopal et al. 54 , observed a higher grain yield and available N content in soil under S. aculeata co-culture in direct seeding.
The interaction between planting geometry or cultivar and weed management tactics significantly influenced the grain yield.The treatment P S and H H + W H combination achieved the highest grain yield, followed by P S and H H + S c , P N and H H + S c , and P N and H H + W H (Table S1).Among weed management and cultivar interactions, the highest grain yield was observed for Arize 6444 × H H + W H and Arize 6444 × H H + Sc combinations (Table S2).Better crop growth, higher dry matter accumulation, and greater weed suppression ability of the Arize 6444 cultivar with square planting and hand hoeing fb hand weeding or hand hoeing fb Sesbania spp.co-culture could be the reasons for the higher grain yield.
Planting geometry, cultivar, and weed management had a significant impact on production efficiency.The results showed that square planting (P S ) had the maximum production efficiency compared to zero-till seed drillsown crops (P N ).The higher yield with square planting could be attributed to improved production efficiency.www.nature.com/scientificreports/Among cultivars, Arize 6444 resulted in higher production efficiency than PHB 71.The H H + W H achieved the highest production efficiency across weed management treatments and was comparable to H H + Sc.The increased crop yield per day was believed to be a reason for the higher production efficiency in H H + W H and H H + Sc.The P S and H H + W H interactions increased production efficiency (Fig. 4c).The cultivar × weed management interaction revealed that maximum production efficiency was recorded for Arize 6444 and H H + W H (Fig. 4d).This could also be because of the higher grain yield ha −1 day −1 and effective weed control 12 .

Economic analysis
A slightly higher cost of cultivation (COC) was registered for P N (600.55US$) compared to P S (591.47 US$), which was due to the higher cost of hybrid seeds used under seed-drill sown crops (Table 5).Square planting had higher gross returns (GR) by 7.24%, net returns (NR) by 15.59%, and B: C ratio of 8.78% than zero-till drill sown crops.This was because of the lower COC coupled with a higher GR in P S than P N .Cultivars did not influence the COC due to similar seed rates, seed costs, and other inputs.However, higher GR, NR, and BCR were obtained for Arize 6444 compared to PHB 71 because of the higher yield under Arize 6444 12,18 .The COC for weed control treatments ranged from 459.46 to 763.22 US$ ha −1 ; W C had the lowest COC and H H + M R6 had the highest.Rice straw was applied at a rate of 6 t ha −1 and the higher cost of rice straw was the reason for the higher COC in the H H + M R6 treatment.Higher GR (1398.26US$ ha -1 ) and NR (851.03US$ ha -1 ) were observed under H H + W H and H H + S C, and the least was with W C in both years.However, BCR was higher for H H + S C fb H H + W H treatment.These results could be the result of lower weed density under H H + W H and H H + S C 14 .The interaction effect between planting geometry × weed management was found to be significant for GR, NR and BCR (Fig. 5a-c).Highest GR, NR, and BCR were recorded under interaction of P s and H H + W H as compared to other treatment combinations.

Conclusions
The results emphasize the importance of selecting appropriate weed management strategies for sustainable DSR, taking into account both environmental considerations and economic feasibility.The findings from this study revealed that Arize 6444, the square planting system, and the hoeing fb hand weeding performed better in terms of yield than PHB 71, normal planting and other weed management practices.However, the higher cost of manual weeding and the unavailability of labors are the main drawbacks of the hoeing fb hand weeding system.Alternatively, Arize 6444, square planting geometry, and hoeing at 12 DAS fb Sesbania co-culture mulch at 45 DAS enhanced the productivity and profitability of DSR and significantly reduced weed density in the Eastern region of India.These findings contribute valuable insights to the ongoing efforts to promote sustainable and www.nature.com/scientificreports/environmental friendly weed management practices, mitigating the risks associated with herbicide use and potential evolution of resistant weeds in direct-seeded rice systems.Development and research on precise seeding machines is a future research area for wider adoption of hybrids in DSR systems, higher weed control efficiency, and higher yield.Additionally, an assessment of the long-term impacts of the proposed weed management strategies on soil health, biodiversity, and overall ecosystem resilience is needed.

Experimental site and weather conditions
Field experiments were carried out at the Agricultural Research Farm of the Institute of Agricultural Sciences, Banaras Hindu University, Varanasi (25,018′ N and 88,003′E), Uttar Pradesh, India, during the rainy seasons (June to October) in 2015 and 2016.The cropping system at the site has been rice followed by wheat for the last six years.The climate of the site is sub-tropical; May and June were the hottest months (maximum temperature 31-36 °C) and January was the coldest month (minimum temperature 7-14 °C).Annual rainfall averages 1036.8 mm and 87.3% of them are received between June and September (South-West Monsoon), and the remaining 13.7% is received between October and May (western disturbances and other climatological factors).

Treatment details and crop management
The experiments were arranged in a split-split plot design with three trial factors (planting geometries, cultivars, and non-chemical weed management) in three replications.Two planting geometries [normal (PN) and square planting (PS)] were arranged in the main-plots, two cultivars (Arize 6444 and PHB 71) in the sub-plots, and five non-chemical weed management treatments [weedy check (WC), single hoeing (1 HH) at 12 DAS fb one hand weeding (1 HW) at 30 DAS (HH + WH), 1 HH at 12 DAS fb Sesbania co-culture and its mulching (HH + Sc), 1 HH at 12 DAS fb rice straw mulching @ 4t ha −1 (HH + MR4), and 1 HH at 12 DAS rice straw mulching @ 6 t ha −1 (HH + MR6)] in the sub-subplots (Table 1).The main plot size was 40 m × 5 m, the sub-plot size was 20 m × 5 m, and the sub-sub plot was 4 m × 5 m.The field was prepared with one pass of moldboard plough fb disk to uproot established perennial weeds.Finally, two passes of cultivator and planking were done to provide a good tilth    suitable for a DSR crop.The sowing dates were June 22, in 2015 and June 28, in 2016.Nitrogen (150 kg ha −1 ), P 2 O 5 (60 kg ha −1 ), and K 2 O (60 kg ha −1 ) were applied at the recommended rates through urea (NH 2 ) 2 CO), diammonium phosphate ((NH4) 2 HPO 4 ) and muriate of potash (KCl), respectively.Half of the recommended nitrogen and full doses of phosphorus and potassium were applied at the time of sowing.The remaining nitrogen was given in two equal portions at the tillering and panicle initiation stages.The crop was harvested manually on 28th October in 2015 and 5th November in 2016 (Table 6).

Weed density and composition
In each plot, two quadrates (1 m 2 ) were placed randomly for weed observations (25 and 60 DAS).Weeds were classified as grass, broadleaf, and sedge after identification.At 60 DAS, the relative density of various weed flora was calculated by dividing the weed density of each weed species by the overall weed density in the weedy check plot and multiplying the result by 100.
where ni is the number of species i, pi is the proportion of the species i in total number of species, N is the total number of individuals in a sample.
where H is the species diversity index (i.e., Shannon-Wiener index), and S is the species richness (number of weed species present in a plot).

Weed control indices
The weed control efficiency indices were calculated using weed dry matter and density data as well as crop dry matter and yield data at 25 and 60 DAS 59,60

Figure 1 .
Figure 1.Interaction effect of planting geometry × weed management on sedge, broadleaf and total weed densities at 25 DAS (a) and broadleaf density at 60 DAS (b).PN, sowing with seed drill at 18.5 cm row spacing; PS, square planting at 25 cm × 25 cm row to row and plant to plant spacing; W0, weedy check (no weed management); HH + WH, one hand hoeing at 12 DAS fb one hand weeding at 30 DAS; HH + SC, one hand hoeing at 12 DAS fb Sesbania aculeata co-culture and mulched 45 DAS; HH + MR4, one hand hoeing at 12 DAS fb rice residue mulching @ 4 t ha −1 ; HH + MR6, one hand hoeing at 12 DAS fb rice residue mulching @ 6 t ha −1 .Means with different alphabets are significant (P < 0.05).Values shown in the figure are square-root [√(x + 0.5)]-transformed means.

Figure 2 .
Figure 2. Interaction effect of planting geometry × weed management and cultivar × weed management on evenness at 25 (a,b) and 60 DAS (c,d).P N , sowing with seed drill at 18.5 cm row spacing; P S , square planting at 25 cm × 25 cm row to row and plant to plant spacing; W C , weedy check (no weed management); H H + W H , one hand hoeing at 12 DAS fb one hand weeding at 30 DAS; H H + S C , one hand hoeing at 12 DAS fb Sesbania aculeata co-culture and mulched 45 DAS; H H + M R4 , one hand hoeing at 12 DAS fb rice residue mulching @ 4 t ha −1 ; H H + M R6 , one hand hoeing at 12 DAS fb rice residue mulching @ 6 t ha −1 .Means with different alphabets are significant (P < 0.05).

Figure 3 .
Figure 3. Interaction effect of planting geometry × weed management and cultivar × weed management on dominance (a,b) and Shannon-Weiner index (c,d) at 60 DAS.P N , sowing with seed drill at 18.5 cm row spacing; P S , square planting at 25 cm × 25 cm row to row and plant to plant spacing; W C , weedy check (no weed management); H H + W H , one hand hoeing at 12 DAS fb one hand weeding at 30 DAS; H H + S C , one hand hoeing at 12 DAS fb Sesbania aculeata co-culture and mulched 45 DAS; H H + M R4 , one hand hoeing at 12 DAS fb rice residue mulching @ 4 t ha −1 ; H H + M R6 , one hand hoeing at 12 DAS fb rice residue mulching @ 6 t ha −1 .Means with different alphabets are significant (P < 0.05).

Figure 4 .
Figure 4. Interaction effect of planting geometry × weed management, and cultivar × non-chemical weed management on number of tillers (a), dry matter production (b) and production efficiency of rice (c,d).P N , sowing with seed drill at 18.5 cm row spacing; P S , square planting at 25 cm × 25 cm row to row and plant to plant spacing; W C , weedy check (no weed management); H H + W H , one hand hoeing at 12 DAS fb one hand weeding at 30 DAS; H H + S C , one hand hoeing at 12 DAS fb Sesbania aculeata co-culture and mulched 45 DAS; H H + M R4 , one hand hoeing at 12 DAS fb rice residue mulching @ 4 t ha −1 ; H H + M R6 , one hand hoeing at 12 DAS fb rice residue mulching @ 6 t ha −1 .Means with different alphabets are significant (P < 0.05).

Figure 5 .
Figure 5. Interaction effect of planting geometry × weed management on gross return, net return and B:C ratio of rice.P N , sowing with seed drill at 18.5 cm row spacing; P S , square planting at 25 cm × 25 cm row to row and plant to plant spacing; W C , weedy check (no weed management); H H + W H , one hand hoeing at 12 DAS fb one hand weeding at 30 DAS; H H + S C , one hand hoeing at 12 DAS fb Sesbania aculeata co-culture and mulched 45 DAS; H H + M R4 , one hand hoeing at 12 DAS fb rice residue mulching @ 4 t ha −1 ; H H + M R6 , one hand hoeing at 12 DAS fb rice residue mulching @ 6 t ha −1 .Means with different alphabets are significant (P < 0.05).

Table 2 .
Effect of planting geometry, cultivar and non-chemical weed management on weed diversity in rice.*Means with different alphabets are significant (p < 0.05).DAS, days after sowing.P N , sowing with seed drill at 18.5 cm row spacing; P S , square planting at 25 cm × 25 cm row to row and plant to plant spacing; W C , weedy check (no weed management); H H + W H , one hand hoeing at 12 DAS fb one hand weeding at 30 DAS; H H + S C , one hand hoeing at 12 DAS fb S. aculeata co-culture and mulched 45 DAS; H H + M R4 , one hand hoeing at 12 DAS fb rice residue mulching @ 4 t ha −1 ; H H + M R6 , one hand hoeing at 12 DAS fb rice residue mulching @ 6 t ha −1 .**Bold P values are significant.

Table 4 .
Effect + W H , one hand hoeing at 12 DAS fb one hand weeding at 30 DAS; H H + S C , one hand hoeing at 12 DAS fb S. aculeata co-culture and mulched 45 DAS; H H + M R4 , one hand hoeing at 12 DAS fb rice residue mulching @ 4 t ha −1 ; H H + M R6 , one hand hoeing at 12 DAS fb rice residue mulching @ 6 t ha −1 .**Bold P values are significant.
of planting geometry, cultivar and non-chemical weed management on growth attributes and yield in rice.*Means with different alphabets are significant (p < 0.05).DAS, days after sowing.P N , sowing with seed drill at 18.5 cm row spacing; P S , square planting at 25 cm × 25 cm row to row and plant to plant spacing; W C , weedy check (no weed management); H H

Table 5 .
Effect of planting geometry, cultivar and non-chemical weed management on cost of cultivation, gross return, net return and B: C ratio.*Means with different alphabets are significant (p < 0.05).DAS, days after sowing.P N , sowing with seed drill at 18.5 cm row spacing; P S , square planting at 25 cm × 25 cm row to row and plant to plant spacing; W C , weedy check (no weed management); H H + W H , one hand hoeing at 12 DAS fb one hand weeding at 30 DAS; H H + S C , one hand hoeing at 12 DAS fb S. aculeata co-culture and mulched 45 DAS; H H + M R4 , one hand hoeing at 12 DAS fb rice residue mulching @ 4 t ha −1 ; H H + M R6 , one hand hoeing at 12 DAS fb rice residue mulching @ 6 t ha −1 .**Bold P values are significant.

Table 6 .
Description of planting geometry, cultivar and weed management options adopted in the experiment.Rice was sown using 30 kg seed ha −1 by tractor-drawn zero till seed drill at a row spacing of 18.5 cm apart 2 P S Rice was sown using 12 kg seed ha −1 by kudal (local furrow maker) manually at 25 cm × 25 cm row to row and plant to plant spacing Sc one hand hoeing was done at 12 DAS fb Sesbania aculeate co-culture (Sesbania aculeata was sown in between rice rows manually by using 25 kg seed ha −1 ).After that Sesbania aculeata was harvested manually with the help of sickle at 45 DAS and green residue was placed in between rice rows 7 H H + M R4 one hand hoeing was done at 12 DAS fb rice straw mulching @4 t ha −1 .Rice straw of last year crop was weighed and spread uniformly just after hoeing in between rice rows 8 H H + M R6 one hand hoeing was done at 12 DAS fb rice straw mulching @6 t ha −1 .Rice straw of last year crop was weighed and spread uniformly in between rice rows just after hoeing